Android Google Maps get Boundary Co-ordinates

You need to use Projection and VisibleRegion classes in order to get visible LatLng region.
So your code would look something like:

LatLngBounds curScreen = googleMap.getProjection()
    .getVisibleRegion().latLngBounds;

In Android(Kotlin) you can find LatLng this way, in every time zoom or. gesture detect

private var mMap: GoogleMap? = null
..........



    mMap?.setOnCameraMoveStartedListener { reasonCode ->
        if (reasonCode == GoogleMap.OnCameraMoveStartedListener.REASON_GESTURE) {
            val curScreen: LatLngBounds =  mMap!!.getProjection().getVisibleRegion().latLngBounds
            var northeast=curScreen.northeast
            var southwest=curScreen.southwest
            var center=curScreen.center
            Log.v("northeast LatLng","-:"+northeast)
            Log.v("southwest LatLng","-:"+southwest)
            Log.v("center LatLng","-:"+center)
        }
    }